If you consider QuickTime 6.1 a bug-fix release, you’ll be very happy — it’s solid a includes lots of small improvements, one of the most significant being a better selection of datarates for AAC encoding. You should upgrade ASAP.
If you were hoping for a new-features release, you may be disappointed. Most seriously, Apple’s claims of MPEG-4 Video quality improvements in its QuickTime 6.1 update appear to be specious. Ben Waggoner, an encoding expert who did the MPEG-4 encoding for the NerdTV challenge I reported on last month, says that the quality of the MPEG-4 Video codec proved “not much better” in preliminary testing.
(As QuickTime 6’s MPEG-4 Video encoder came in dead last in the NerdTV tests compared to other Simple Profile encoders, avoid it for professional work. Instead, use the soon-to-be-relased Sorenson Squeeze for MPEG-4, which is available for both Windows and Macintosh and won a “best of show” award at this week’s Macworld.)
Also, although Apple had promised 3GPP-compliant MPEG-4 support before the end of 2002 and demonstrated content (presumably encoded with QuickTime) playing on a 3GPP-compliant phone at Macworld, I’ve confirmed that QuickTime 6.1 does not support playing or encoding 3GPP-compliant MPEG-4. An Apple representative told Ben that they were forced to delay 3GPP support because their AMR (Adaptive Multi-Rate) speech codec wasn’t ready yet.